Field of the Invention
The present invention relates to a vehicle engine placed, together with a radiator and an intake system, in an engine compartment of a vehicle and more particularly to an apparatus for heating an intake system for an engine of a vehicle with hot or warm water, the engine being configured such that various accessory devices provided in relation to an intake system are heated by circulation of cooling water or coolant (hot water) heated or warmed by cooling the engine.
Related Art
As the above type of technique, conventionally, there has been known an air control device disclosed in for example Japanese unexamined patent application publication No. 7-77108(1995) (JP-A-7-77108(1995)). In an engine, generally, outside or ambient air is directly taken into a combustion chamber through an intake passage. In cold areas, therefore, cold outside air is directly drawn into an intake passage and may cause freezing of various accessory devices provided in the intake passage. Herein, examples of the accessory devices provided in the intake passage may include a throttle valve, a mixer located before a compressor of a supercharger, and others. In even an engine provided with an EGR device, water or moisture in EGR gas flowing therein through the EGR passage may freeze near the throttle valve. Conventional accessory devices are therefore configured to circulate cooling water (hot water), which has been heated or warmed by cooling the engine, to heat the accessory devices to prevent their freezing. The device described in JP-A-7-77108(1995) is configured such that a throttle shaft and its surrounding parts as well as the throttle valve are warmed together by the hot water. It is herein conceived that a flow of the hot water to heat the accessory devices is controlled by opening and closing a hot water control valve provided in a hot water passage. This hot water control valve is also conceivably controlled according to the temperature of the hot water or the temperature of each of the heated accessory devices.